Gordon Brown was losing control of his cabinet reshuffle today as it emerged that Jacqui Smith, Britain's first female home secretary, and two other government ministers planned to quit the frontbench.

In a turbulent day for the prime minister, Tom Watson, the Cabinet Office minister, and Beverley Hughes, the families minister, also let it be known that they would leave the government in the shakeup, pre-empting Brown's planned overhaul of his frontbench team, due to come after the European and local elections.

Smith, who has been at the centre of intense controversy over her expenses claims, apparently told Brown two months ago that she did not want to continue in office.

She is said to have been "hurt" by recent events, which have included the revelation that she inadvertently claimed for two pornographic films watched by her husband and criticism of the way she has designated a house she shares with her sister in London as her main home.

The move will pave the way for a overhaul of Brown's cabinet following what is expected to be disastrous election results for Labour this weekend.

With the future of Alistair Darling, the chancellor, also in doubt, the revelation led to opposition claims that the government was in disarray. William Hague, the shadow foreign secretary, said the government was "just a row of political corpses". He went on: "Half of the cabinet are working out how to cling on to their jobs and the other half are working out how to get out of them."

But accusations of chaos were denied by Harriet Harman, the leader of the Commons, who told Radio 4's The World at One: "It's not the wheels falling off government."

Smith, who had been widely tipped for the sack, appears to have decided that she would rather resign on her own terms. After Sky broke the news that she was going to resign, a source close to her said that she had discussed her plans to stand down with the prime minister two months ago. "She's been hurt by what's gone on and it's been a difficult couple of months for her," the source said.

Smith, who was chief whip before her surprise appointment as home secretary when Brown became prime minister, has had a difficult two years in the post. The Home Office is a notorious graveyard for political careers and since 1997 two of her predecessors – David Blunkett and Charles Clarke – have been forced out against their will.

Her expenses claims are currently the subject of an investigation by the parliamentary commissioner for standards. She repaid £10 claimed for the pornographic films, but in other respects she has insisted that she has done nothing wrong.

Smith also faces a very tough battle to hold on to her Redditch seat, where she had a majority of 2,716 at the last election. Boundary changes have left her with an even smaller notional majority of 1,948.

The news broke as three other Labour MPs – David Chaytor, Patricia Hewitt and Beverley Hughes – announced that they would be standing down at the next election. Chaytor has already lost the whip after claiming £13,000 for a mortgage that did not exist, but Hewitt and Hughes said their decisions had nothing to do with revelations about their expenses.

Chaytor, Ian Gibson, Margaret Moran and Elliot Morley were all told by a Labour panel today that they would be banned from standing for the party at the next election. Gibson is the only one of the four MPs who had not already announced he would step down. Reports this evening said he would stand down at the election, too.

In a letter to Brown, Hughes said she wanted to leave government because she wanted "to be at home much more than being a minister or MP will ever allow".

Watson, a close ally of Brown's, also let it be known that he wanted to leave the government at the reshuffle. He is known to be concerned about the impact politics is having on his family life, and he was particularly hurt when he was falsely accused of collaborating with Damian McBride in the "smear" email affairs. Watson knew nothing about the emails that led to McBride's resignation as a Downing Street aide.

The reshuffle, which is expected very soon after Thursday's elections, is also likely to see Alistair Darling replaced as chancellor. Ed Balls, the children's secretary, is seen as the candidate most likely to replace Darling and one possibility is that Darling, a long-standing friend of Brown's, may replace Smith at the Home Office.

David Miliband, the foreign secretary, has been seen as a potential candidate for the Home Office or the Treasury. But he told a news conference today that he wanted to remain in his post and beat Ernest Bevin's six-year record as Labour's longest-serving foreign secretary.

Smith attended this morning's cabinet meeting – almost certainly her last as home secretary. At around 3.40pm she opened a debate in the Commons for the second reading of the borders, citizenship and immigration bill, although in her opening remarks she made no comment about her future.

Chris Grayling, her Tory shadow, noted that this was Smith's "final appearance at the dispatch box" and congratulated her on being the first female home secretary. He added that her decision to "preannounce the reshuffle" would doubtless cause "consternation in Downing Street".

In her interview on The World at One, Harman described the reports about Smith's future as "speculation". She also paid tribute to her colleague.

"I think she makes an excellent contribution to the House of Commons. I think she is an outstanding home secretary," the leader of the house said.

"Yes, there has been controversy about her expenses, and she is not alone in that. But I don't think she has ever wavered from her commitment to her job as home secretary, and indeed she was in cabinet carrying out her duties this morning.

"She is a very conscientious woman who takes her responsibilities very seriously."

Without confirming that Smith would be leaving government, Harman also said that ministers leaving the government was a "normal process".

Ben Wallace, the Tory MP who submitted a complaint about Smith to the parliamentary commissioner for standards, told the programme: "[Smith's resignation] was on the cards, but what I think is amazing is the total collapse in management of the government. Some are going now, some people are jumping ship without even informing the prime minister, it looks like."